| Abstract
| - Large quantities of arsenic are introduced into theenvironment through land application of poultry littercontaining the organoarsenical feed additive roxarsone (3-nitro-4-hydroxyphenylarsonic acid). The objective of thisstudy was to evaluate the bioconversion of roxarsone andrelated N-substituted phenylarsonic acid derivativesunder anaerobic conditions. The results demonstrate thatroxarsone is rapidly transformed in the absence ofoxygen to the corresponding aromatic amine, 4-hydroxy-3-aminophenylarsonic acid (HAPA). The formation of HAPAis attributable to the facile reduction of the nitro group.Electron-donating substrates, such as hydrogen gas, glucose,and lactate, stimulated the rate of nitro group reduction,indicating a microbial role. During long-term incubations,HAPA and the closely related 4-aminophenylarsonic acid(4-APA) were slowly biologically eliminated by up to 99%under methanogenic and sulfate-reducing conditions, whereaslittle or no removal occurred in heat-killed inoculumcontrols. Arsenite and, to a lesser extent, arsenate wereobserved as products of the degradation. Freely soluble formsof the inorganic arsenical species accounted for 19−28% of the amino-substituted phenylarsonic acids removed.This constitutes the first report of a biologically catalyzedrupture of the phenylarsonic group under anaerobicconditions.
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